The HYSYS Process Simulation Software - Engineering Assignment Help

Assignment Task

Task

To undertake this coursework, you will need to use the HYSYS process simulation software available on the Engineering Virtual Desktop and the Autocad Virtual Desktop from your personal computer.
Your submission part A should include:
A single pdf file (no more than 2 pages, excluding title page) containing the answers to each of the coursework questions except question 1. Title your submission pdf file: PS1 AZ
A copy of the HYSYS case file detailing the simulation model and results used to answer questions 1-5 on the coursework sheet. Title your submission HYSYS file: Case 1 A
3. A copy of the HYSYS case file detailing the simulation model and results used to answer question 6 on the coursework sheet. Title your submission HYSYS file: Case 2 A
Your submission part B should include:
1. A single pdf file (no more than 2 pages, excluding title page) containing the answers to each of the coursework questions except question 1. Title your submission pdf file: PS1 B
A copy of the HYSYS case file detailing the simulation model and results used to answer questions 1-5 on the coursework sheet. Title your submission HYSYS file: Case 1 B
3. A copy of the HYSYS case file detailing the simulation model and results used to answer questions 6 and 7 on the coursework sheet. Title your submission HYSYS file: Case 2 B
DO NOT include any screenshots or graphs from HYSYS in your coursework (pdf file). Marks will be deducted if you do.
Coursework part A : Multicomponent distillation
In a gas processing facility, a hydrocarbon mixture (HC Mix) is compressed to 445 psia and then cooled down to -30°F before it passes to the NGL fractionation section of the plant where it is firstly fed to a de-ethaniser. The HC Mix stream has the following characteristics (use imperial (Field) units):
Stream HC Mix
Temperature 21°F
Pressure 350 psia
Component Molar flowrate (lbmol/h)
Hydrogen 2400
Methane 1000
Ethane 1900
Ethylene 2700
Propane 85
Propene 180
n-Butane 40
n-Hexane 13
To simulate the de-ethaniser, use the Shortcut Column for initial estimates and then the Distillation Column to effect a separation whereby 99.99% of the ethane (light key) in the feed is recovered in the overheads and 95% of the propene (heavy key) is recovered in the bottoms. Assume the following:
• Hydrogen, methane and ethylene are fully recovered in the overheads
• Propane, n-butane and n-hexane are fully recovered in the bottoms
• The pressure at the bottom and the top of the column is 438 psia and 430 psia, respectively.
• External reflux ratio, R = 1.2 Rmin • Full Reflux condenser
• Once-through, regular Hysys reboiler
• Zero pressure drop in all heat exchangers
Questions :1. Build a process flowsheet to represent the process described above by adding the appropriate unit operation models from the HYSYS model palette, making sure that you connect the units in the direction of the main stream flow to avoid any calculation errors. Make sure that both column simulations (Shortcut Column & Distillation Column) are included in the same flowsheet.
2. Select an appropriate physical property package for your simulation and explain the rationale behind this choice.
3. For the Shortcut Column, what is the molar fraction of the light key in the bottoms and the molar fraction of the heavy key in the overheads? Explain in your submission how you have determined these, including any calculations or a Hysys model/flowsheet (this should be in the main flowsheet and appropriately labelled) .4. What is the minimum reflux ratio, number of stages, and the optimal feed stage calculated in the Shortcut Column? What is the reflux ratio, reboiler and condenser duties calculated in the Distillation Column?
5. a) Using the appropriate logical operation in HYSYS, investigate and demonstrate (with appropriate graphs) how the reflux ratio affects the number of stages as well as the reboiler and condenser duties of the de-ethaniser. The product recoveries should remain the same and your investigation should be limited to a maximum R = 1.5 Rmin. Which column unit (Shortcut or Distillation) will you use to carry out this investigation and why?
b) What are the design and economic implications of decreasing the reflux ratio of a column (do not use simulations or calculations to answer this)?. Cite and include references (in a separate reference list at the end of the document), if you used any.
6. For the Distillation Column, use the Adjust operation to determine the reflux ratio required to achieve a propene recovery of 97% in the bottoms. Submit this as a separate flowsheet.
Coursework instructions part B: Reactors
Ammonia is produced by reacting nitrogen from air with hydrogen during the Haber-Bosch process. Hydrogen is usually obtained from steam reforming of methane, and nitrogen is obtained from deoxygenated air. The chemical reaction that takes place in vapour phase using a catalyst is shown below:
????2 + 3????2 ? 2????????3
You are asked to produce a simulation for the production of ammonia using Aspen HYSYS. You will create a very simplified version of this process shown in the process flow diagram below (Figure 1).

You are asked to produce three different flowsheets within the same HYSYS case/file:
1. Ammonia synthesis flowsheet as above using an isothermal Conversion Reactor
2. Ammonia synthesis flowsheet as above using an isothermal Equilibrium Reactor
3. Ammonia synthesis flowsheet as above using an isothermal PFR Information on the process streams and unit operations is provided below:
Fluid package: Peng-Robinson
Stream SynGas:
Temperature 280°C
Pressure 26.52 bar
Flowrate 7000 kmol/h
Component Molar fraction
Hydrogen 0.7371
Ammonia 0
CO 0.0024
Argon 0.0027
Methane 0.0103
Nitrogen 0.2474
Make-up Gas Compressor
Outlet pressure: 275 bar
Mixer
Keep default settings.
Heater
Pressure drop: 0.1 bar
Outlet temperature: 450°C
-Note that for some of the flowsheets, this heater is initially acting as a cooler, but once we connect the recycle stream this block will in fact add heat and raise the temperature of the stream.
Reactor (Conversion)
Pressure drop: 0 bar
40 % conversion of nitrogen
Reactor (Equilibrium)
Pressure drop: 0 bar
Equilibrium constant, Keq = 1.64×10-4 (fixed)
Reaction basis: Activity
Reactor (PFR)
The kinetic rate law for the ammonia synthesis reaction is as follows (partial pressures are in atm):

The pressure drop across the bed of catalytic particles can be estimated using the Ergun equation. Assume spherical catalyst particles. The reactor and catalyst specifications are provided below:

Cooler
Pressure drop: 0.1 bar
Outlet temperature: 26.85°C
Valve (this is not shown in the flowsheet above but needs to be added between the cooler and the separator)
Pressure drop: 50 bar
Separator
Keep default settings.
Purge
You need to use the Tee unit for this and assume that 1% of the vapour stream of the separator is purged (in other words 0.01 flow ratio for stream Purge under Design | Parameters page of this unit).
You should include a Recycle unit after the Purge unit and before the Recycle Compressor to facilitate convergence. Marks will be deducted if this is not included.
Recycle Compressor
Outlet pressure: 275 bar
Questions
1. Build a process flowsheet for each reactor unit to represent the process described above by adding the appropriate unit operation models from the HYSYS model palette, making sure that you connect the units in the direction of the main stream flow to avoid any calculation errors. Make sure that all three ammonia synthesis flowsheets (Conversion, Equilibrium and PFR) are included in the same HYSYS case/file.
2. For the Equilibrium Reactor flowsheet, investigate and demonstrate (with appropriate graphs) the effect of the inlet temperature of the separator on the production rate of ammonia (ammonia flowrate in liquid outlet of separator) using the appropriate logical operation in HYSYS. Discuss and explain briefly the results.
3. For the PFR flowsheet, what is the reactor conversion (%) before you close the recycle loop? Compare this with the reaction conversion calculated when you complete the flowsheet (i.e. when the loop is closed). Is the closed loop conversion higher or lower and why?
4. After you complete the PFR flowsheet, look at the Message Window at the bottom of your screen. Why are you getting a warning message by HYSYS about the Heater (heat exchanger before reactor) being actually a cooler (message should say:“Temperature decrease on heating”)? Why are you not getting the same message for the other two reactor flowsheets?
5. a. What is the production rate of ammonia (kmol/h) in the Equilibrium Reactor outlet? If the operating temperature of this reactor is reduced to 430°C, is the resulting ammonia production rate the same or different than before? Explain briefly why.
5 b. What happens if you do the same for the Conversion Reactor? Does the ammonia production rate change if you decrease the temperature to 430°C in this case? Explain briefly why.
6. What is the ammonia molar fraction in the liquid outlet of the separator for the Conversion Reactor flowsheet? Using the Adjust operation, determine the purge ratio required to achieve 95.5% molar fraction of ammonia at liquid outlet stream of the separator.
7. a. For the PFR flowsheet, use the Spreadsheet operation to calculate the space time (in seconds) for the packed bed reactor. Include all the formulas and calculations in your answer (calculated value should be rounded to 2 decimal places).
b. Using the Adjust operation, determine the reactor length required to have a space time of 15 seconds.

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